The hunt for the elusive 11th starter on defense will be in full swing this week, according to Mike Nolan. The second-year head coach is searching for answers after his defense played poorly once again in the 17-7 loss Saturday night against Dallas.

With Moore missing the Dallas game, rookie Melvin Oliver started at defensive end, and Oliver looked lost at times. The 49ers allowed 189 rushing yards to the Cowboys.

Nolan hopes a shakeup will improve tackling, a problem in the last two games.

"We often had a lot of guys around the ball, but we didn't make the play," Nolan said. "At first, I thought we might have lined up wrong. ... Tackling and pass rush are the two areas that seem to stand out the last two weeks that we need to do a better job of."

Other changes: With offensive lineman Adam Snyder sidelined over the past two weeks with a biceps injury, Kwame Harris will start the season at right tackle and Justin Smiley will be the right guard.

"Adam will continue to push those guys," Nolan said. "He could unseat somebody during the season."

Nolan also said that both safety spots were open, meaning Tony Parrish is being challenged at strong safety. Parrish is returning from a broken leg sustained in October, which might have contributed to his late arrival when trying to help Sammy Davis on deep passes Saturday night.

"I don't want to make an excuse for anyone," Nolan said when the Parrish injury was mentioned. "It was either (the injury) or slow recognition. Whatever the reason, it plays into our decision on who starts and who doesn't."